For two days, Sara Keenan had no smartphone and no contact with the online world Sign up to Simon Calder’s free travel email for expert advice and money-saving discounts Get Simon Calder’s Travel email Get Simon Calder’s Travel email Email * SIGN UP I would like to be emailed about offers, events and updates from The Independent. Read our Privacy notice As I place my phone in a small lockbox for the next 48 hours, I laugh nervously at my friends. Outwardly, I’m joking. Inwardly, I feel a